Control apparatus, method of controlling the same, and communication system

ABSTRACT

A control apparatus operable to control a plurality of access points (APs) configured to be able to use joint beamforming (JB) includes a memory containing instructions, and at least one processor for executing the instructions. The executed instructions cause the control apparatus to obtain, from a station (STA) which is a communication partner, reception information on a received signal strength at the STA of signals transmitted from the plurality of Aps, and determine, based on the reception information, a communication parameter related to JB for communication with the STA. It is determined to use JB for communication with the STA in a case where there is one or more other received signal strengths for which a strength difference from a largest received signal strength among a plurality of received signal strengths of the plurality of APs included in the reception information is within a predetermined range.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to control of communication that usesjoint beamforming.

Description of the Related Art

As communication standards for a wireless local area network (WLAN),standards of the IEEE 802.11 series are known. US-2018-0084584 proposesa technique for making it possible to secure high frequency utilizationefficiency while suppressing interference in communication using IEEE802.11ax.

To further improve throughput, an Extreme High Throughput (EHT) StudyGroup (SG) was established in IEEE in 2018. In the EHT SG, a techniquecalled Joint Beamforming (JB) has been proposed. JB is a technique aimedat improving the reachable distance of signals by causing collaborativeoperation of a plurality of Access Points (AP). Specifically, the samedata is transmitted on the same frequency channel at the same time whileadjusting the phase with respect to the same Station (STA).

Incidentally, in general, when a plurality of APs are placed atdifferent positions, reception intensity of radio waves arriving fromrespective APs observed at a certain STA are different from each other.There is a problem that, when only the reception intensity of a radiowave that arrives from a certain AP is relatively large, improvement ofthe reachable distance by using JB cannot be expected, while resourcesof the entire system are wastefully consumed.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a control apparatusoperable to control a plurality of access points (APs) configured to beable to use joint beamforming (JB), comprises: an obtaining unitconfigured to obtain, from a station (STA) which is a communicationpartner, reception information on a received signal strength at the STAof signals transmitted from the plurality of APs; and a determining unitconfigured to determine, based on the reception information, acommunication parameter related to JB for communication with the STA.

The present invention enables efficient use of joint beamforming (JB).

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a diagram illustrating an overall configuration of a wirelessnetwork system.

FIG. 2 is a diagram illustrating a hardware configuration of eachapparatus.

FIG. 3 is a flowchart of an operation in an STA.

FIG. 4 is a flowchart of an operation in an AP control apparatus.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe attached drawings. Note, the following embodiments are not intendedto limit the scope of the claimed invention. Multiple features aredescribed in the embodiments, but limitation is not made of an inventionthat requires all such features, and multiple such features may becombined as appropriate. Furthermore, in the attached drawings, the samereference numerals are given to the same or similar configurations, andredundant description thereof is omitted.

First Embodiment

As a first embodiment of the control apparatus according to the presentinvention, a communication system configured to be able to use JointBeamforming (JB) will be exemplified and described below.

<System Configuration and Apparatus Configuration>

FIG. 1 is a diagram illustrating an overall configuration of a wirelessnetwork system that includes an AP control apparatus 101 which is acontrol apparatus according to the first embodiment. An STA 104 is acommunication apparatus having a role as a station (STA) thatparticipates in a wireless network. The APs 102 and 103 arecommunication apparatuses that each have a role as an access point (AP)that builds a wireless network. Although FIG. 1 exemplarily illustratesa wireless network configured by two APs and one STA, the number of APsand STAs is not limited to this.

Each communication apparatus supports communication that uses jointbeamforming (hereinafter simply referred to as JB), and can executecommunication via a wireless network. Each communication apparatus cancommunicate in frequency bands of the 2.4 GHz band, the 5 GHz band, andthe 6 GHz band. Also, each communication apparatus can communicate usingbandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz.

By executing OFDMA communication, each communication apparatus canrealize multi-user (MU) communication in which signals of a plurality ofusers are multiplexed. In OFDMA communication, a part of a dividedfrequency band (RU: Resource Unit) is allocated to each STA so they donot overlap with each other, and the carriers of each STA areorthogonalized. Therefore, the AP can communicate with a plurality ofSTAs in parallel.

As described above, each communication apparatus is configured to beable to use JB. That is, the two APs 102 and 103 can performcollaborative operation to communicate with the STA 104. The AP controlapparatus 101 controls the APs 102 and 103 and performs communicationcontrol using JB, as described later. FIG. 1 illustrates an example inwhich the APs 102 and 103 are communicatively connected to the APcontrol apparatus 101 via a backhaul line so that the APs 102 and 103can communicate with each other for collaborative operation. However,the function of the AP control apparatus may be configured to beincorporated into any one AP of a plurality of APs.

It is sufficient if each communication apparatus is compliant with astandard of the IEEE 802.11 series (802.11a/b/g/n/ac/ax/be). In additionto a standard of the IEEE 802.11 series, other communication standardssuch as Bluetooth (registered trademark), NFC, UWB, ZigBee, and MBOA maybe supported. Here, NFC is an abbreviation of Near Field Communication,UWB is an abbreviation for Ultra Wide Band, and MBOA is an abbreviationfor Multi Band OFDM Alliance. UWB include wireless USB, wireless 1394,WiNET, or the like. Further, configuration may be taken to support acommunication standard of a wired communication such as a wired LAN.

Specific examples of the APs 102 and 103 include, but are not limitedto, wireless LAN routers or PCs. The APs 102 and 103 may each be awireless chip or the like that is capable of executing wirelesscommunication based on the wireless LAN standard.

A specific example of the STA 104 includes, but is not limited to, acamera, a tablet, a smart phone, a PC, a mobile phone, a video camera,or the like. In addition, the STA 104 may be a wireless chip or the likethat is capable of executing wireless communication based on thewireless LAN standard.

FIG. 2 is a diagram illustrating a hardware configuration of eachapparatus. That is, a hardware configuration of the AP control apparatus101, the APs 102 and 103, and the STA 104 is exemplarily illustrated.Each apparatus includes a storage unit 201, a control unit 202, afunction unit 203, an input unit 204, an output unit 205, acommunication unit 206, and an antenna 207. Configuration may be takensuch that the AP control apparatus 101 has only the communication unit206 for wired communication and does not have the antenna 207. Further,the APs 102 and 103 may each be configured to have a communication unit206 corresponding to both wired communication and wirelesscommunication.

The storage unit 201 is configured by a memory such as a ROM or a RAM,and stores various information such as a computer program for performingvarious operations to be described later, communication parameters forwireless communication, and the like. ROM is an abbreviation of ReadOnly Memory and RAM is an abbreviation of Random Access Memory. As thestorage unit 201, a storage medium such as a flexible disk, a hard disk,an optical disk (CD, DVD, or the like), a magneto-optical disk, amagnetic tape, or a nonvolatile memory card may be used in addition to amemory such as a ROM or a RAM. The storage unit 201 may be configured bya plurality of memories.

The control unit 202 is configured by one or more processors such as aCPU and an MPU, for example, and controls the entire apparatus byexecuting a computer program stored in the storage unit 201. CPU is anabbreviation of Central Processing Unit, and MPU is an abbreviation ofMicro Processing Unit. The control unit 202 may control the entireapparatus in cooperation with computer programs stored in the storageunit 201 and the OS (Operating System). In addition, the control unit202 generates data and signals to be transmitted in communication withother apparatuses. In addition, the control unit 202 may include aplurality of processors such as with multi-cores, and the entireapparatus may be controlled by the plurality of processors.

The function unit 203 is hardware for the apparatus to executepredetermined processing. The function unit 203 realizes a functionunique to each apparatus through control in accordance with the controlunit 202. For example, the STA 104 executes processing such as imaging,printing, and projecting in addition to radio communication. Inaddition, the APs 102 and 103 execute processing for transferring thereceived data and setting processing for communication, which isdescribed later. The AP control apparatus 101 executes a process relatedto setting for communication for the APs 102 and 103.

The input unit 204 receives various operations from a user. The outputunit 205 performs various outputs with respect to the user via a monitorscreen or a speaker. Here, the output by the output unit 205 may bedisplayed on a monitor screen, an audio output by a speaker, a vibrationoutput, or the like. It should be noted that both the input unit 204 andthe output unit 205 may be realized by one module as in a touch panel.The input unit 204 and the output unit 205 may be integrated together orbe apparatuses that are separate from each other.

The communication unit 206 performs communication with other devices.The data to be communicated includes user data (image data, documentdata, video data, or the like) and control data (data related tocommunication settings). As described above, the AP control apparatus101 may be configured to include only the communication unit 206 forwired communication. Further, the APs 102 and 103 may each be configuredto have a communication unit 206 that supports both wired communicationand wireless communication. The communication unit 206 which is forwireless communication controls the antenna 207 to transmit and receivea wireless signal for wireless communication generated by the controlunit 202. Note that, in addition to a wireless LAN standard, when an NFCstandard, a Bluetooth standard, or the like is supported by theapparatus, the apparatus may control wireless communication based onthese communication standards. In addition, configuration may be suchthat, in the case where wireless communication conforming to a pluralityof communication standards can be executed, the apparatus has separatecommunication units 206 and antennas 207 which conform to respectivecommunication standards.

In the present embodiment, it is assumed that the STA 104 is configuredto be able to connect to a wireless network configured by one or both ofthe AP 102 and the AP 103. It is assumed that, when the STA 104 isconnected to a plurality of APs, the AP control apparatus 101 controlsthe respective APs to perform operation for JB.

<Issues for Communication Using JB>

JB is a technique aimed at improving a reachable distance of a signal byallowing a plurality of access points (APs) to transmit the same data onthe same frequency channel at the same time while adjusting the phasewith respect to the same station (STA). Each of the plurality of APs cantransmit using a maximum transmission output which is regulated by radiowave regulations of each country. Therefore, by a plurality of APstransmitting after performing collaborative operation (adjustingphases), the radiation intensity in a specific direction can be madelarger than that which can be output by a single AP. For example, whenthe two APs operate in cooperation with each other, an improvement inradio wave intensity of about a maximum of 6 dB is expected under anideal situation, and the reachable distance is expected to approximatelydouble. However, depending on the positional relationship between theplurality of APs and the STA, there are cases where JB cannot beeffectively used and the reachable distance cannot be extended.

For example, in order to actually improve the signal strength by about 6dB, it is necessary for the signals of the respective APs to reach theSTA to be communicated with at the same strength. If the signalstrengths from the respective APs differ by 10 dB, the improvement ofthe signal strength in accordance with JB can be expected to be onlyabout 1 dB. Although a method of decreasing the signal strength of theAP on a side where a signal strength is stronger to align the signalstrengths is also conceivable, the effect is limited as compared with acase where the AP on the side where the signal strength is strongertransmits a signal to the STA alone. Therefore, when the signalstrengths from the respective APs are greatly different from each other,it is considered that it is more efficient to not perform JB from theviewpoint of resource consumption.

Further, when the STA is close to any of the APs and is at a positionwhere a signal to noise ratio (SNR) can be sufficiently ensured, amaximum effective communication rate can be realized without using JB.In such a case, it is also better to not to perform JB.

An exemplary situation in which the use of JB is effective is when theAPs 102 and 103 are relatively close to each other, and in contrast tothis the STA 104 is far apart from the APs 102 and 103. Since the STA104 is distant from both APs, an adequate effective communication ratecannot be ensured. On the other hand, since the difference between thedistance from the STA 104 to the AP 102 and the distance from the STA104 to the AP 103 is relatively small, strengths of signals from each APare substantially equal at the STA 104.

<Operation of the Apparatus>

Next, the operation for a communication connection in the presentembodiment will be described with reference to FIGS. 3 and 4. FIG. 3 isa flowchart of operation in the STA 104, and FIG. 4 is a flowchart ofoperation in the AP control apparatus 101.

In step S301, the STA 104 connects to a wireless network configured bythe AP control apparatus 101. More specifically, it connects to awireless network formed by the AP 102 or the AP 103. Here, descriptionis given assuming that the STA 104 establishes a connection with one AP(the AP 102). As a result, the STA 104 enters a state in whichcommunication with the AP control apparatus 101 via the AP 102 becomespossible.

In step S302, the STA 104 periodically measures a received signalstrength indicator (RSSI) as reception information of a signal from theAP 102 and the AP 103. For example, the RSSI of beacon signalstransmitted from the AP 102 and the AP 103 is measured. Here, it isassumed that the RSSI of signals from one or more connectable APs (herethe AP 102 and the AP 103) is measured, but the RSSI of signals fromother APs may be further measured.

In step S303, the STA 104 notifies the AP control apparatus 101 of themeasured result of RSSI. For example, the STA 104 performs anotification when it detects that the beacon transmitted from the AP 102includes information indicating that the AP 102 can use JB.Configuration may be taken such that the STA 104 transmits a measurementresult (RSSI notification) to the address of the AP control apparatus101 which has been notified to the STA 104 in advance. Alternatively,configuration may be taken such that the STA 104 transmits an RSSInotification to the AP 102 to which it is currently connected, and theAP 102 transfers the RSSI notification to the AP control apparatus 101.

In step S401, the AP control apparatus 101 receives and obtains, fromthe STA 104, the RSSI notification, which is reception information atthe STA 104 which is the communication partner. That is, the RSSInotification transmitted from the STA 104 in step S303 is received viathe AP 102 which is communicably connected to the STA 104 in advance.Note that a signal such as a beacon includes, as an IP address,information of a transmission source indicating which AP the signal isfrom. Thus, the STA 104 can know which AP the RSSI corresponds to. Here,when the STA 104 makes an RSSI notification to the AP control apparatus101, it notifies the AP control apparatus 101 of which AP the RSSI isfor.

In step S402, the AP control apparatus 101 determines the largest RSSIof the one or more RSSIs included in the received RSSI notification.Further, it is determined whether or not the determined largest RSSI isequal to or less than a predetermined threshold (hereinafter, athreshold RSSI) at which a predetermined communication rate can berealized. Here, it is assumed that the threshold RSSI is set in advancein the AP control apparatus 101. If the determined largest RSSI exceedsthe threshold RSSI (step S402→No), the process proceeds to step S405,and if it is equal to or less than the threshold RSSI (step S402→Yes),the process proceeds to step S403.

In step S403, the AP control apparatus 101 determines whether or notanother AP, for which a strength difference, with respect to the largestRSSI determined in step S402, is within a predetermined range, ispresent in the received RSSI notification. Here, it is assumed that thepredetermined range is set in advance in the AP control apparatus 101.If there is another AP whose strength difference is less than or equalto the predetermined range (step S403→Yes), the process proceeds to stepS404, and if there are no other AP whose strength difference is lessthan or equal to the predetermined range (step S403→No), the processproceeds to step S405.

In step S404, the AP control apparatus 101 determines that it ispossible to expect improvement of a communication range or acommunication speed, in accordance with JB. Therefore, the AP controlapparatus 101 determines to use JB for communication with the STA 104,and controls the respective APs so as to perform communication via aplurality of APs (here, the AP 102 and the AP 103). Specifically, eachAP is notified to perform JB in which a plurality of APs are used forwhich a strength difference of RSSIs is within a predetermined range.

In step S405, the AP control apparatus 101 determines that it is notpossible to expect improvement of a communication range or acommunication speed, in accordance with JB. Therefore, the AP controlapparatus 101 determines not to use JB for communication with the STA104, and notifies each AP so as to perform communication via one AP(here, the AP 102). That is, when the processing has proceeded from stepS402 to step S405, it is possible to expect that a sufficientcommunication rate can be ensured without using JB, and furtheroptimization of communication in accordance with JB is limited. Further,when the processing has proceeded from step S403 to step S405,optimizing communication in accordance with JB is limited bycombinations of available APs.

In step S304, the STA 104 waits for a signal from the AP controlapparatus 101 notifying transitioning to JB. If notified (Yes in stepS304), the processing proceeds to step S305, and if not notified (No instep S304), the processing proceeds to step S306. Here, the case wherethe notification of the transition to JB is not given includes a casewhere a notification for independent communication is made.

In step S305, the STA 104 transitions to communication that uses JB.Specifically, the AP 102 and the AP 103 receive a transfer function thatis estimated in the AP control apparatus 101 and start communicationwith the STA 104. It is necessary to obtain a transfer function betweeneach AP and the STA 104 in order to implement JB. In order to obtain atransfer function, channel state information (CSI) between each AP andthe STA 104 is required.

Therefore, the STA 104 transmits a sounding frame, which is a frame forcalculating CSI, prior to performing JB. The AP 102 and the AP 103 cancalculate CSI with the STA 104 by receiving the sounding frame.Alternatively, the AP 102 and the AP 103 transmit sounding frames. TheSTA 104 can calculate CSI with the AP 102 and the AP 103 by receivingthe sounding frame.

When the CSI is calculated in the AP 102 and the AP 103, the AP 102 andthe AP 103 notify their calculated CSI to the AP control apparatus 101.In contrast, when the CSI is calculated at the STA 104, the STA 104notifies the calculated CSI to the AP control apparatus 101. As aresult, the AP control apparatus 101 can estimate a transfer functionbetween each AP (the AP 102 and the AP 103) and the STA 104, and the APcontrol apparatus 101 notifies each AP of the estimated transferfunction. Each of the AP 102 and the AP 103 starts communication withthe STA 104 using the notified transfer function. As a result,communication using JB is realized.

In step S306, the STA 104 communicates via one of the APs. Here, it isassumed that communication via the currently connected AP 102 iscontinued, but there may be a switch to communication via another APthat is designated by the AP control apparatus 101.

As described above, according to the present embodiment, the RSSI of thesignals transmitted from the plurality of APs is measured by the STA,and parameters of JB communication are determined based on the resultsof RSSI measurements. With this configuration, more efficientcommunication can be realized. Specifically, when the effect of using JBis limited, the consumption of resources of the entire system can besuppressed by performing control so as to not use JB. Further, in thecase of using JB, it is possible to clearly determine a combination ofAPs capable of maximizing an effect.

Although the present embodiment does not mention whether or not MIMO(Multiple-Input and Multiple-Output) is performed, similar effects canbe obtained by performing a similar process as the present embodimenteven when MIMO is performed. Both single-user (SU)-MIMO and multi-user(MU)-MIMO can be used for MIMO operation.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2019-083215, filed Apr. 24, 2019 which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A control apparatus operable to control aplurality of access points (APs) configured to be able to use jointbeamforming (JB), comprising: a memory containing instructions; and atleast one processor for executing the instructions to cause the controlapparatus to: obtain, from a station (STA) which is a communicationpartner, reception information on a received signal strength at the STAof signals transmitted from the plurality of APs; and determine, basedon the reception information, a communication parameter related to JBfor communication with the STA, wherein it is determined to use JB forcommunication with the STA in a case where there is one or more otherreceived signal strengths for which a strength difference from a largestreceived signal strength among a plurality of received signal strengthsof the plurality of APs included in the reception information is withina predetermined range.
 2. The control apparatus according to claim 1,wherein the communication parameter includes information on whether touse JB for communication with the STA.
 3. The control apparatusaccording to claim 1, wherein the communication parameter includesinformation for designating APs to be used for communication using JBwith the STA.
 4. The control apparatus according to claim 1, whereinprior to obtainment of the reception information by the obtaining unit,the STA has established a communication connection via one AP of theplurality of APs, and the obtaining unit obtains the receptioninformation from the STA via the one AP.
 5. The control apparatusaccording to claim 1, wherein it is determined not to use JB forcommunication with the STA in a case where the largest received signalstrength exceeds a predetermined threshold.
 6. The control apparatusaccording to claim 5, wherein it is determined to use JB forcommunication with the STA in a case where the largest received signalstrength is less than or equal to the predetermined threshold.
 7. Thecontrol apparatus according to claim 6, wherein the instructions arefurther executed to determine an AP corresponding to the largestreceived signal strength and one or more APs corresponding to the one ormore other received signal strengths as a plurality of APs to be usedfor communication using JB with the STA.
 8. The control apparatusaccording to claim 7, wherein the instructions are further executed to:estimate a transfer function based on channel state information (CSI)between the STA and the plurality of APs to be used for communicationusing JB with the STA, and notify the estimated transfer function to theplurality of APs to be used for communication using JB with the STA. 9.A method of controlling a control apparatus operable to control aplurality of access points (APs) configured to be able to use jointbeamforming (JB), the method comprising: obtaining, from a station (STA)which is a communication partner, reception information on a receivedsignal strength at the STA of signals transmitted from the plurality ofAPs; and determining, based on the reception information, acommunication parameter related to JB for communication with the STA,wherein, it is determined to use JB for communication with the STA in acase where there is one or more other received signal strengths forwhich a strength difference from a largest received signal strengthamong a plurality of received signal strengths of the plurality of APsincluded in the reception information is within a predetermined range.10. A communication system comprising a plurality of access points (APs)configured to be able to use joint beamforming (JB), a control apparatusfor controlling the plurality of APs, and a station (STA), the systemcomprising: a memory containing instructions; and at least one processorfor executing the instructions to cause the communication system to:measure a received signal strength of signals transmitted from theplurality of APs, transmit reception information relating to themeasured received signal strength to the control apparatus, obtain thereception information from the STA, determine, based on the receptioninformation, a communication parameter related to JB for communicationwith the STA, and set communication with the STA based on acommunication parameter received from the control apparatus, wherein itis determined to use JB for communication with the STA in a case wherethere is one or more other received signal strengths for which astrength difference from a largest received signal strength among aplurality of received signal strengths of the plurality of APs includedin the reception information is within a predetermined range.
 11. Anon-transitory computer-readable recording medium storing a programmaking a computer execute a method of controlling a control apparatus tocontrol a plurality of access points (APs) configured to be able to usejoint beamforming (JB), the method comprising: obtaining, from a station(STA) which is a communication partner, reception information on areceived signal strength at the STA of signals transmitted from theplurality of APs; and determining, based on the reception information, acommunication parameter related to JB for communication with the STA,wherein it is determined to use JB for communication with the STA in acase where there is one or more other received signal strengths forwhich a strength difference from a largest received signal strengthamong a plurality of received signal strengths of the plurality of APsincluded in the reception information is within a predetermined range.